While virtually all cells are fated to die, very little is known about the molecular mechanisms responsible for senescence and death. This proposal outlines experiments to characterize the genes which mediate cell death during development. These experiments arise from our studies of-the intersegmental muscles (ISM) of the tobacco hawkmoth Manduca sexta, which die during a 36 hour period in response to a defined endocrine trigger. We have isolated cDNA clones for 4 genes that-are expressed when the ISM become committed to die, and three that are repressed. A range of molecular approaches will be used to isolate, sequence and express additional cell death genes. In particular, we are interested in characterizing transcriptional regulators which initiate the cell death process. Insect muscle fibers will be injected with one of the following molecules generated from our clones: anti-sense transcripts, sense transcripts, antibodies, purified expressed proteins or recombinants made with a reporter gene fused to putative cell-death gene promoters. We will utilize the fly Drosophila for a genetic analysis of the cell death process. Molecules isolated from -insects will be used to examine cell death during vertebrate neurogenesis. It is clear that that examination of such model systems will provide basic insight into the molecular mechanisms which mediate senescence and death in animal cells.